Examination of an annular system of underdamped Josephson junctions in the presence of external radiation showed that the ability of the system to lock with some external radiation was determined not only by the number but also by the type of rotating excitations (fluxons or antifluxons). Shapiro steps can be observed in the current-voltage characteristic only in the system with trapped fluxons or in the system with fluxon-antifluxon pairs. If the trapped fluxons circulate simultaneously with fluxon-antifluxon pairs, there are no Shapiro steps regardless of the amplitude or frequency of the applied external radiation.

中文翻译：

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交流驱动环形约瑟夫森结：缺少的夏皮罗步骤

在存在外部辐射的情况下，对欠阻尼的约瑟夫逊结的环形系统进行检查，结果表明，系统锁定某些外部辐射的能力不仅取决于旋转激发的数量，而且取决于旋转激发（激子或反激子）的类型。仅在具有被束缚的通量的系统中或在具有通量-反通量对的系统中，才能在电流-电压特性中观察到Shapiro阶跃。如果捕获的通量与通量对反通量对同时循环，则无论施加的外部辐射的幅度或频率如何，都没有Shapiro阶跃。